Process for electrolyzing fused metallic salts



mom ALREHCUB mu l -1mm I we FOR ElLEGTRQLYZING FUSED METAEJLEEE nit-swor Original application med e u 10, nice, Serial Ho. ssieoe' filed February 5, ficriel; We. comers.

To all whom it may concern:

lie it known that I, EDGAR ARTHUR Ase chorus subject of the King of Great But ain, residing at 32 Liverpool Street, in the city of'lLondon, England, have invented new and useful Improved Processes for Electrolyzing- Fused Metallic Salts, of which the following is a specification.

My invention consists principally 111 an improved process for electrolyzing fused metallic salts and recovering the metals and acid radicals therefrom, and is more especielly intended for use in the-electrolysis of metallic chlorides such as chloride of zinc, or chloride of lehd, and the recovery of the metal and chlorine.

My process can also be employed in the treatment of metal-bearing ores and other materials which when chlorinated yield metallic chloride, the said chloride (after being purified if necessary) being then sub jected to electrolysis for recovery of the metal and chlorine.

, separately the metallic a d gaseous uctsof the electrolysis, The electrodes may,

lily invention is hereinafter described as applied to the electrolysis of zir chloride, but I may use it for the dr'omposition of any other suitable salt and also for the production of alloys from mixtures of chic rides, or other suitable salts and for the re covery oi? yuluahle-constituents from metalbearing ores and 'materials.

Hitherto in the electrolysis of fused salts separate couples have been employed, each couple consisting of an anode of carbon, or graphite, and a fused-metaL cathode arranged within a container for the fused materials.

According to my present invention the electrolysis of the fused salt, or salts, for the separation and recovery of the metallic and other components, is effected in a multiple couple electrolyzer comprising a series of closely-spaced electrodes all immersed in the same body of molten electrolyte. This electrolyte may be contained in a lBfIflG- tory, and preferably hcat-insulated, conteiner, only the first and last of the electrodes being connected with the electric supply conductors. The inner wall of the contamer surrounds, or embraces, the series of electrodes, thus preventing-eacessive leakage 0 current past the edges, and passages are provided for leading oli crease the conductivity,

the edges of prod )Diyidcd and one application if desired, be all of the same composition, for example of compressed carbon, or graphits, and any convenient number of couples may be employed, the opposed surfaces of any two adjacent electrodes-and the inter-- vening space filled with electrolyte constituting What I term a couple.

Apparatus fulfilling the requirements of the process according to my present invention is described and illustrated in the specification of my application for Letters Patent'Serial No. 551,306 filed April 10, 1922. For the purpose of description I will presume that zinc chloride is treated.

lhe fused zinc chloride, preferably at a temperature of about 350 to 400 centigrade as this prevents fuming of the fused salt is introduced into the said apparatus.

During electrolysis the electrolyte is maintained at a temperature between 420 and. 600 centi'grade, preferably 450 to 500 eentigrade. If it be desired to in- I may add to the zinc chloride a suitahle proportion of chloride of potassium, chloride of sodium, or chloride of magnesium. The-apparatus is fed With zinc chloride to replace that decomposed by the current and in this manner the said apparatus can be worked con tinuously for a long time. The fusion of the electrolyte may he maintained by means of the electric current, and external heat may be applied to the container, as hereinafter explained. The fusion may also be maintained Wholly, or in part, by applying a supplementary alternating current to the first and last electrodes of the electrolyzer, such current being more economically produced than the continuous current necessary for electrolysis.

The electrolysis sets free zinc (in the case instanced) on the upper surfaces of the electrodes and a corresponding Weight of chlorine on their under surfaces. The zinc flows downwards into a reservoir. cl'ilorine rises to the upper part of the apparatus and the said zinc and chlorine do not come again. into contact after being separated loy the current. Satisfactory circulation ofthe electrolyte throughout the an i paratus is caused by the upward flow or the gas and the dO'WH'WEIq'llflOW oi? the metal The use of the invention results energy, the use of process according to my 11" economy of electrical a more convenient Wfifill r' 'Iil energy required to D" o mist-rue on working and ugokcep of the epperctus.

"illieoeeticclly the chemical volsege rcquircrl for tile (lccompositirm of zinc Cl'llfi' riclc in a. state of fusion is appi'oximcmly 1.6, volts and the faccdeic yield, per ampere iiour, 1.21% grams; i icrc'fiore the minimum loclucc one kilogi'um of zinc is 1315" watt-l": =urs ixclusiveof that needed to keep Ethe eleccrolyie in the molten condition For technical reasons it is preferable to keep the clecerolyte fused. by interncl electrical heafiing due to extra terminal voltage, or to a supplemencai'y alternating current, It follows that efficicnt iueuleticn ic e prime factor in economy. It is necesfiery in single-couple cypcz'etue to em loy high current deneily, and the loss of met through the electrodes is considerable; consequently, in the best form of singlecouplc apparatus the terminal voltage per couple ie believed to be approximately three times 'ihe neccccarychemical. volioge, and Willi a currentefiiciency of 90 per cent the energ efficiency cz mioi'z be ifiifltil much above $30 per cent. The lower the current dci'icity cmi'iloywl 2395 the electrodes, with a view in securing low bcrminal voltage, the more accentuated are ll'ie difficulties of racticcl heat conservation such (lillicultiec cing clue to tile incrcescil size and inconvenientform of the apparatus designed for such a purpose it is usually found that the eco comical lower limit of current density is about four, in six, emperors pier equine inch of clcct -oilc surface, and. greater current (icusitics have often been employed.

My aforesaid multipic-couple elcctrolyzcr enables current densities of from two ampei'es to one iimperc, and even less, per square incl: of electrode mirfucc, to be employed, cm! :1 low tcrmimil voltage per couple to no oliicincd.

In the following claims although the process awording in his inven sicn is more especially (l'ircrrtml to the clectrolysisof zinc chloride and lcml chloride the expression metallic call, includes not only thee? cults, but. any metallic salt to which the process ie applicable and it also covere mixtures of mclaillc salts, and the expreceion metallic chloride also covers mixtures of meeellic chlorides.-

/Vliat I claim is:---

l. the process of electrolyzing fused lic cult-s, the step of decou'iposing the mitencously at electrolytic couples -=l series below the surface of the iclvciiolyle. 4

In clue process o-.=-eleeteclyzing fused metallic suite, the step of decomposing the melt cimuliux'iccuely electrolytic couples in electrical so; below the eurfece of the fused elec trolyc, and gathering libei'etcd.

c eee fused electrolyte, 11ml circulatingthe fused electrolyte iQl'H'Ougli the actiou of a product of iecompositiouh In the process of clectrolyzing fused metallic salts, the step of decomposing the melt simultaneously at electrolytic coupl 5 in electrical series below the surface of t e fused eiecirclyte, and causing the liberated products of decomposition to pass in opposed directions through the fused electrolyte and thereby effect its circulatiom 6-. In the process of clectrolyzing fused metallic salts, the step of decomposing the melt simultaneously at electrolytic couples in electrical series below the surface of the fused electrolyte, and meintzrining an equiv ble temgaeraturc in the zone of electrolysis by causing products of clccomposifiion to cf fect a circulation of the fused electrolyte.

7. in the procese of electrolyzin lused metallic salts, the step of decomposing the meltsimultaneously at electrolytic couples in electrical series below the surface of the fused electrolyte, and substfintially confining the flow of electric cur ent'to the im-' merserl electrode areas and 'ehe fused electrolyte 'tl'iercbciwecn in order to minimize.

currentleakage.

-8. In the process; of 'electrolyzing fused metallic salts, the step of decomposing flee melt simultaneously at electrolytic couples in electrical series below the surface oi the fused electrolyte, and heating the fused melt by sup lying thereto current at 3 voltage above 12 e .sum ofthe several voltages requisite to eal'ect electrolytic decomposition at the several couples. 8. In the process of electrolyzing fused metallic/salts, tli step of decomposing the melt eimultaneouly at electrolytic couples in electrical series below the surface of the fused electrolyte, moo varying the temperature of the fused melt by varying the voltage supplied thereto above the sum of' the several voltages requisite to efiect electro 'lyeic decomposition at the several electrolytic coupl.ee,--

10. In the process of electrolyzieg fused meiallic ealcs, elfecting multiple couple electrolysis of the fused melt at a ccrminal volt-- of less than 8.5 volts er couple.

lb 11; film process of eieccrolyzingz fused menses 'met'allic salts, effecting multiple couple electrolysis of the fused melt at a current density of not more than two ampcres per square inch ot-electrode surface in contact with the melt.

12. In the process of elcctrolyzing-fused metallic salts, the step of decomposmg the melt simultaneousl at electrolytic couples in electrical series slow the surface of the fused electrolyte, and minimizing heat radiation from the melt.

13. In the process of electrolyzing fused metallic salts, the step of decomposing the melt simultaneously at electrolytic couples in electrical series below theisurface of the fused electrolyte, and supplying external heat to the fused melt.

14. In the process of electrdlyzing fused. metallic salts, the steps offeeding the fused salts in a fluid condition but below fuming temperature to an electrolytic apparatus and efi'ecting series multiple couple electrolysis of the melt in said apparatus.

15. In the process of electrolyzing fused metallic salts, the step of decomposing the melt simultaneously at electrolytic couples dividing the fused melt bv a group of close-' ly spaced electrodesinunersed therein, and efiect'ing'th'e simultaneous electrolysis of the meltbetw'een adjacent electrodes by passing current in series through the several electrodes and the intervening layers of fused electrolyte.

18. The metho metallic salt'iter the recovery of metal and acid radicle therefrom, which comprises subd of decomposing a fused dividing the fused inelt by a' group of close- 1y spaced electrodes--immersed therein, ef

fecting the simulta neous electrolysis of the a melt between adjacentelectrodes by passing current in ;series through the several electrodes 'andthe intervening layers of fused electrolyte, and separately recuperating the metal and the acid radicle resulting from the decomposition.

19. The method of treatin metal bearing material, which comprises-c lorinatingthe same to obtain metallic chloride therefrom, leading said chloride in fused condition to electrolytic apparatus, and effecting series multiple couple electrolysis of the chloride therein.

20. The method of treating metal *bearing material which comprises chlorinating the same to obtain metallic chloride therefrom, leadin said chloride in fusedlcondition to electro ytic' apparatus, and efl'ectin series multiple couple electrolysis-of the chloride i therein, and -recuperating separately the metal and acid radicle resulting from electrolytic decomposition. I I

In testimony whereof I have'signed my name-to this specification in the-presence of a subscribing witness.

EDGAR ARTHUR ASHCROFT Witness:

G. F. TYsoN. 

